1.Field of the Invention
The present invention relates to an optical pickup for recording information signals on an optical disk or reproducing information signals from the optical disk, and an optical disk apparatus using the optical pickup.
2.Description of the Related Art
FIG. 7 shows a schematic constitution of a general optical disk apparatus. In FIG. 7, reference numeral 1 denotes an optical disk, reference numeral 2 denotes an optical head, and reference numeral 3 denotes a spindle motor for rotary-driving the optical disk 1. The optical head 2 is constituted by a laser light source 6, a collimator lens 7, a beam splitter 8, a condenser lens 9, a light receiving element 10, an objective lens 20, and an actuator 11 for performing the focus control and the tracking control of the objective lens 20.
The optical disk 1 is constituted by an information signal recording layer 13 composed of a phase changing material reversibly changeable in a phase state formed on a substrate 12 and a cover layer 14 composed of a transparent resin material. A spiral or concentric recording track is formed on the information signal recording layer 13. The information signal recording layer 13 may be made of an optical magnetic recording material or a metal reflection film having pits (concavities and convexities) thereon. The optical pickup 2 is installed at the side opposing to the cover layer 14 of the optical disk 1. An optical beam for recording or an optical beam for reproduction is irradiated to the optical disk 1 from the optical pickup 2, thereby performing the recording and reproduction of the information signal.
FIGS. 8A and 8B show constitutions of the actuator 11. FIG. 8A is an oblique view, and FIG. 8B is a side view. The actuator 11 is composed of a fixed part 26 and a movable part 25. The fixed part 26 is constituted by permanent magnets 21a, 21b, and 21c, a yoke 24, and support base 17. The movable part 25 is constituted by an objective lens 20, focus coils 19a and 19b, a tracking coil 18, and a lens supporting member 15 for supporting these parts.
Elastic supporting members 16a, 16b, 16c, 16d, 16e, and 16f are linear and elastic, and have high conductivity. One end of each elastic supporting member is fixed to the support base 17, and the other end is fixed to the side surface of the lens supporting member 15 so that the movable part 25 is freely displaceable in a focus direction, tracking direction and radial and tilt direction with respect to the optical disk 1.
Here, a winding wire terminal 28 of each of focus coils 19a and 19b and a tracking coil 18 is entwined with a terminal protrusion 27 provided at the side surface of the lens supporting member 15. The elastic supporting members 16a, 16b, 16c, 16d, 16e and 16f are soldered (22) to the focus coils 19a and 19b and the tracking coil 18 on the terminal protrusion 27, so that they are electrically connected to the coils. With respect to the winding wire terminals 28, the winding wire terminal of the tracking coil 18 is entwined with the upper most terminal protrusion from among the terminal protrusions of the lens supporting member 15, and the winding wire terminal of the focus coil 19a is entwined with a second terminal protrusion, and the winding wire terminal of the focus coil 19b is entwined with a third terminal protrusion.
Further, as shown in FIG. 7, the optical disk apparatus includes an error signal generation circuit 4 and a control circuit 5 for performing a focus control, a tracking control and a tilt control of the actuator 11. The control circuit 5 provides a control current to the focus coils 19a and 19b and the tracking coil 18 through the elastic supporting members 16a, 16b, 16c, 16d, 16e and 16f. 
The control circuit 5 supplies a control current based on a focus error signal and a tracking error signal to the focus coils 19a and 19b and the tracking coil 18. The actuator 11 drives the movable part 25 in three directions for the optical disk 1 by an electromagnetic force generated between this control current and a magnetic flux generated by the permanent magnets 21a, 21b and 21c. The three directions mean a focus direction for the optical disk 1, a tracking direction orthogonal to the recording track, and a radial tilt direction with a tangential direction of the recording track taken as an axis.
In this manner, even if the optical disk 1 is displaced in the focus direction by axial runout, an optical spot follows this displacement and is focus-controlled so as to accurately focus on the recording track. Further, even if the recording track is displaced in the tracking direction by radial runout, the optical spot is track-controlled so that it scans, while following this displacement. Further, the optical spot is tilt-controlled so as to compensate the influence of a disk tilt and the like.
By the way, in recent years, since the optical disk apparatus has been applied to portable instruments, for example, a recording and reproduction instruments of voices, still images, moving images and the like, the smaller size and thinner size of the optical disk apparatus have become important issues. However, in the conventional optical pickup, a size of height direction of the lens supporting member of the actuator movable part greatly depends on the layout of the terminal protrusion.
For example, Japanese Patent Application Laid-Open No. 2000-57603 discloses that a plurality of the terminal protrusions 27 integrally molded with the lens supporting member as shown in FIG. 9 are arranged at each of both sides of a plain orthogonal to the optical disk including a tangent line of the recording track in the position of the optical spot of the optical disk 1. Each terminal protrusion 27 of one side thereof protrudes in the same direction from the same surface of the lens supporting member 15, and it is, therefore, necessary to give consideration to a winding wire jig space and a soldering space within the same plane.
FIG. 10 shows a side view of a coil winding wire terminal part of the lens supporting member. The winding wire 28 of each coil is rotated and wound around the terminal protrusion 27 by the winding wire jig, and therefore, it is necessary to arrange adjacent terminal protrusions at a predetermined interval (approximately 1 mm or more) so that the winding wire jig and the terminal are prevented from interfering with each other. The winding wire jig is a jig for automatically winding the winding wire 28 on the terminal protrusion 27, and for example, as shown in FIG. 10, a winding wire jig of an approximately Φ1 mm rotates around the terminal protrusion 27, thereby winding the winding wire 28 on the terminal protrusion 27. The range shown by diagonal lines in FIG. 10 becomes a layout space for the winding wire jig.
Further, in order to solder one end of the elastic supporting member to the terminal protrusion 27, a predetermined space is required at a side where the terminal is soldered. Due to limitation on the assembly of these parts, the adjacent terminal protrusions are required to be arranged usually at the interval of approximately 1 mm or more. The interval between the terminal protrusions generates a trouble when making the lens supporting member of the actuator thin.
FIG. 11 shows a schematic illustration where the lens supporting member is made thin while maintaining the terminal interval (approximately 1 mm) as described above. As shown in FIG. 11, among the three terminal protrusions 27 at one side, the uppermost terminal is referred to as an upper terminal, the terminal in the center as a center terminal, and the lowermost terminal as a lower terminal. In this case, as shown in FIG. 11, in order to make the actuator thin, when the lower terminal is moved upward the focus ((1) of FIG. 11), it is necessary to move the center terminal either to tangential forward or backward directions.
When the center terminal is moved to the tangential forward direction, there arises a problem of interference with a mirror which is an optical component part of the optical pickup or an optical base ((2)(a) of FIG. 11). In order to avoid this problem of interference, relocation of component parts of the optical pickup is required, but because the entirety of the optical pickup is enlarged, thereby making it impossible to make the optical pickup smaller.
Further, when the center terminal is moved to the tangential backward direction, the support point of the elastic supporting member is moved backward, so that the distance between the support point of the movable part side and the fixed end of the fixed part side is shortened((2)(b) of FIG. 11). In this case, sensitivity of the actuator is deteriorated, and the increase of the tilt and the like are caused, and hence, the characteristics of the optical pickup are prone to deteriorate. Thus, in this manner, the layout of the terminal protrusion has caused a trouble when attempt is made to make the actuator thin.